1. Field of the Invention
Detergency as applied to the washing of fabrics, involves both the removal of undesired matter from the fabric and the prevention of redeposition on the fabric. It is known that dirt which is removed from fabrics during a washing operation is suspended in the wash water and tends to redeposit on the fabric. Under appropriate conditions, dirt removed from one fabric in a mixed load can deposit on a clean portion of a second fabric to make the second fabric appear less clean than before washing.
In the past, the preponderance of washable fabrics in common use consisted of cotton of various types. Redeposition of soil on cotton has long been recognized as a problem, which, however, was related primarily to particulate soil. It has been known for some time that this problem with respect to cotton fabrics can be ameliorated by the use of sodium carboxymethyl cellulose.
With the growing popularity of polyester fabrics, alone and in the form of blends, a laundering problem due to difficulties with both removal and redeposition of oily soil has developed. Since sodium carboxymethylcellulose does not affect oily soil redeposition, there is a need to alleviate this problem with polyester fabrics by some other means.
The polyester fabrics and most other synthetic fabrics are more hydrophobic than is cotton. Consequently, there is a greater tendency for oily soils to deposit on the great majority of synthetic fabrics than on cotton. The redeposition characteristics of spun Dacron are considered to be representative of those of the polyester fabrics.
The most pertinent prior art known to applicants is set forth below.